def calc_num_of_sequence_diff_1(length: int) -> int:
    return length * (length + 1) // 2


def main():
    N = int(input())
    A = list(map(int, input().split()))

    A_slide = A[1:]
    A_floor_diff = [A_slide_elm -
                    A_elm == 1 for A_slide_elm, A_elm in zip(A_slide, A)]

    current_idx = 0
    length = len(A_floor_diff)
    sequence_num = 0
    while current_idx < length:
        try:
            current_idx = A_floor_diff.index(True, current_idx)
        except ValueError:
            break

        try:
            current_end_idx = A_floor_diff.index(False, current_idx)
        except ValueError:
            sequence_num += calc_num_of_sequence_diff_1(length-current_idx)
            break

        sequence_num += calc_num_of_sequence_diff_1(
            current_end_idx-current_idx)
        current_idx = current_end_idx

    print(sequence_num)


if __name__ == "__main__":
    main()